Microphone array processing that efficiently collects sounds such as voice and music using a plurality of microphones (microphone array) has been devised and widely used. Generally, the frequency characteristics and gain characteristics of microphones are not the same and vary depending on individuals due to individual differences during manufacturing, changes with time, installation environments, or other factors. Since the sound collection performance degrades when there are differences in the frequency characteristics and gain characteristics of microphones to be used in microphone array processing, the signals obtained from the microphones are corrected to eliminate the differences between the characteristics of the microphones.
There is a method that generates sounds for calibration (calibration sounds) using a sound source device such as a speaker and, based on the signal of the calibration sounds obtained by microphones, corrects the obtained signals to eliminate variations between the characteristics of the microphones. However, this method requires a sound source device generating calibration sounds. On the other hand, there is proposed a method that, using signals obtained by microphones from sounds reaching the microphones, especially the sounds to be collected (referred to below as target sounds) such as voice, corrects the signals itself successively so as to eliminate the differences between the characteristics of the microphones without using a sound source device (PTL 1).